The present invention relates to a variable displacement swash plate compressor.
Japanese Laid-Out Patent Publication Nos. 2-19665 and 5-172052 describe conventional variable displacement swash plate compressors (hereafter simply referred to as the compressors). The compressors each have a housing including a suction chamber, a discharge chamber, a swash plate chamber, and pairs of cylinder bores. A rotatable drive shaft is supported in the housing. A swash plate that is rotatable together with the drive shaft is arranged in the swash plate chamber. A link mechanism is located between the drive shaft and the swash plate to allow the inclination angle of the swash plate to change. The inclination angle refers to an angle relative to a direction orthogonal to the rotation axis of the drive shaft.
Each cylinder bore pair accommodates a piston. The piston is reciprocated in the cylinder bore pair and defines compression chambers in the cylinder bore pair. Each cylinder bore pair includes a first cylinder bore, which is located at a first side, or front side, of the swash plate, and a second cylinder bore, which is located at a second side, or rear side, of the swash plate. Each piston includes a first head, which reciprocates in the first cylinder bore, and a second head, which is formed integrally with the first head and which reciprocates in the second cylinder bore.
A conversion mechanism coverts rotation of the swash plate to reciprocation of the piston in each cylinder bore pair. The stroke when the piston reciprocates is in accordance with the inclination angle of the swash plate. The inclination angle of the swash plate is changed by an actuator, which is controlled by a control mechanism.
The compressors described in Japanese Laid-Out Patent Publication Nos. 2-19665 and 5-172052 each include a pressure regulation chamber in a rear housing member, which is an element of the housing. A cylinder block, which is also an element of the housing, includes a control pressure chamber, which is in communication with the pressure regulation chamber. The actuator is located in the control pressure chamber. The actuator is not rotated integrally with the drive shaft.
In the same manner as each second cylinder bore and each second head, the actuator is located at the second side, or rear of the housing. The actuator includes a non-rotation movable body that covers the rear end of the drive shaft. The non-rotation movable body includes an inner wall surface that supports the rear end of the drive shaft so that the rear end is rotatable. The non-rotation movable body is movable along the rotation axis of the drive shaft. Although the non-rotation movable body moves in the control pressure chamber along the rotation axis of the drive shaft, the non-rotation movable body is not allowed to rotate about the rotation axis of the drive shaft. A spring that urges the non-rotation movable body toward the front is arranged in the control pressure chamber or the pressure regulation chamber. The actuator includes a movable body, which is coupled to the swash plate and movable along the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotation movable body and the movable body. A pressure control valve, which changes the pressure of the control chamber, is arranged between the pressure regulation chamber and the discharge chamber. A change in the pressure of the control pressure chamber moves the non-rotation movable body and the movable body in the axial direction of the drive shaft.
A link mechanism, which is located in the swash plate chamber, includes a movable body and a lug arm, which is fixed to the drive shaft. The rear end of the lug arm includes an elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction intersecting the rotation axis of the drive shaft. The front of the swash plate is supported by a pin inserted through the elongated hole so that the swash plate is pivotal about a first pivot axis.
In the compressor of Japanese Laid-Open Patent Publication No. 5-172052, the front end of the movable body also includes an elongated hole that extends in a direction orthogonal to the rotation axis and in a direction intersecting the rotation axis. The rear end of the swash plate is supported by a pin inserted through the elongated hole so that the swash plate is pivotal about a second pivot axis, which is parallel to the first pivot axis.
In each of these compressors, the pressure control valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the front. Thus, the inclination angle of the swash plate increases, the piston stroke is lengthened, and the compression displacement is increased for each rotation of the drive shaft. When the pressure control valve closes to disconnect the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the rear. Thus, the inclination angle of the swash plate decreases, the piston stroke is shortened, and the compressor displacement is decreased for each rotation of the drive shaft.
Further, in each of these compressors, when the inclination angle of the swash plate changes, the link mechanism is configured so that the top dead center of the first head of each piston is shifted by a greater distance than the top dead center of the second head. More specifically, when the inclination angle of the swash plate is changed, the top dead center of the second head of each piston remains at substantially the same position but the top dead center of the first head is shifted over a relatively long distance to another position. Thus, as the inclination angle of the swash plate approaches zero degrees, each piston slightly performs compression with the second head and does not perform compression with the first head.
In each of these conventional compressors, the actuator is located at the second side of the swash plate, that is, the same side as the second cylinder bores as viewed from the swash plate. Thus, in these compressors, it is difficult to provide open space in the housing at the second side of the swash plate to allow for forward and rearward movement of the non-rotation movable body and the movable body. Further, since the size of the actuator is limited in the radial direction, displacement control is difficult. Moreover, when enlarging the housing in the radial direction so that the inclination angle of the swash plate is easily changed, it may become difficult to install the compressor in a vehicle or the like.